<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>变量-布尔类型</title>
</head>
<body>
    <script>
        var str = "hello world";
        // 非空字符进行布尔判断时会被理解为布尔值 true
        if(str){
            alert("值为真");
        }
        </script>
</body>
</html>